I've had the Nordic Components +2 mag extension on my SuperNova tactical for about 6 months now. I've put quite a few shells through it, stripped the gun and taken everything apart, and never any problems. $80 was a lot, but IMO it was worth it on a Benelli.
From what I've personally seen with the TacStar, I've seen one actually blow off the end of somebody's shotgun (it was a 870) on the range. And I've seen the TacStar mag extensions thread not match up too well with the Benelli SuperNova. I had this problem and so did my friend, so we returned them and went with Nordic. I didn't look into the Choate because at the time they were over $100.